The Iraqi military and its allies have been pushing for a week toward the city of Mosul, held by the Islamic State. For people fleeing the fighting, a few thousand so far, it's been an unbelievably frightening seven days.

In the Debaga camp for displaced people, about 50 miles southeast of Mosul, which is becoming more crowded, I sit with a family who tell me about leaving the village where they lived under ISIS more than two years.

"We left at sunrise, around 4 a.m., and there was no ISIS around. The [Iraqi] security forces were on the outskirts, but hadn't gone in," said a heavily pregnant woman, surrounded by her cousins and their small children, asleep or listless in the hot sun.

The army said it would wait until the civilians were out before attacking ISIS. The extremists banned cellphones on pain of death but secretly some villagers spoke to the army and agreed on an escape route.

But as they were leaving, "ISIS appeared out of nowhere...They were firing at us," said the pregnant woman, who told her story on condition of anonymity because she is afraid of ISIS.

They ran for their lives. And no wonder she is afraid: the men firing were her neighbors – people from the same small village. By her estimate, about half the men in her village pledged allegiance to the extremists.

All politics is local. In her village, the same woman explained, you have to understand there are two tribes — the Shammout and Qufaa.

"It's half the Shammout tribe and half the Qufaa tribe. And the Qufaa joined ISIS. And the Shammout – before ISIS came — they were recruits in the security forces," she said, adjusting the mattress she and the children were clustering under for shade.

Reading between the lines, it seems perhaps one tribe held the security forces jobs and cut the other tribe out of them. When ISIS came along, they exploited that rift. And now the tribesmen they recruited are hardcore ISIS fighters.

"They have tunnels that go all the way to other areas. They are able to smuggle weapons, food and fighters," she said.

She says ISIS members are like rats, living underground. They can melt away and then come back. The fighters have sent their families to other ISIS-held areas for safety. And she thinks it will be very difficult to defeat them.

Across the courtyard, another family is willing to talk, but are also too afraid of ISIS to be identified. I'm speaking only to women because the men are detained, undergoing checks for possible links to ISIS.

These women are from a different village, Ibrahim al-Khalil. But, clustered together around a matriarch with traditional face tattoos, they tell a similar story. The Iraqi army is in their village now, but they won't go back home anytime soon.

They say they're still afraid of ISIS. They won't say which tribes in their area are with ISIS, but they do say some of their relatives are still under the control of the extremists.

"Families are still besieged by ISIS in Mosul," says one of the women, "We have our aunts there, our cousins. We are afraid they will kill them."

Officials from Iraq, and from the U.S., which is supporting the offensive, say ISIS is losing territory and much of the population has turned against the group.

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